A standard single-lever flow-control valve has a fixed valve plate formed with a pair of inlet ports respectively connected to hot- and cold-water inlet lines and, offset therefrom, an outlet port connected to an outlet line normally leading to a faucet. A movable valve plate sitting atop this fixed valve plate has a mixing cavity open toward the fixed plate and movable to variously overlap the ports. When the movable plate is pivoted about a normally upright axis perpendicular to the interface between the plates it can align more of one of the inlet ports with the mixing cavity and less of the other inlet port to vary the ratio of hot and cold water fed to the outlet port, and when slid in a front-to-back direction parallel to the plate interface it can control the overall extent of overlap to vary the overall flow from the inlet ports through the mixing cavity to the outlet port.
Typically the movable valve plate is pivoted on the bottom end of a lever that is centrally pivoted on a housing liner that is coupled to the movable plate to rotate it about the upright axis. The upper end of the lever is fitted to a handle that is raised and lowered to control volume rate of flow and that is pivoted from side to side to control outlet temperature.
It is known from European patent application 0,392,441 of P. Scheffer to provide an extra outlet port for a second user, that is so that the same mixing valve can feed, for example, a faucet constituting a first user and a shower constituting a separate second user. The lever must be thrown to one side or the other to control the respective user, normally working in 180.degree. offset positions for the two users. Thus such a mixing valve can only be mounted where there is ample room to move and manipulate its actuating lever. Furthermore the displacement through 180.degree. to change users is inconvenient even when there is enough room to do it.
In European 0,309,443 of C. Dagiantis such a valve is shown which has three valve disks and that can supply two different users. This arrangement is quite complex, prone to leakage, and expensive to manufacture.